1. Field of the Invention
The present invention relates to a thermal transfer sheet used in an image formation method wherein laser light is used to form high resolution images. Specifically, the present invention relates to a thermal transfer sheet that prevents decreased optical density and deterioration of hues caused by large amounts of heat generated by laser light.
2. Description of the Related Art
Conventionally, a thermal transfer sheet in which a light-heat conversion layer which absorbs laser light and generates heat and also includes light-heat conversion dyestuff such as those which absorb infrared light, and an image formation layer into which a colorant is dispersed, are disposed in that order on a support, is known as a recording material used in a transfer image formation method in which laser light is used. Examples of the thermal transfer sheet include a sublimation-type transfer sheet in which a sublimation dye is used in an image formation layer and a melt-type thermal sheet containing an organic pigment which can melt. In these thermal transfer sheets, at the time of recording, large amounts of heat generated by the laser light may cause the colorants in the image formation layer to decompose, and as a result optical density may decrease and the desired hues cannot be obtained.
In an attempt to solve these problems, a sublimation-type thermal transfer sheets in which sublimation dyes having specific structures and which do not decompose due to heat generated at the time of recording are disclosed in the specifications of Japanese Patent Nos. 2676541, 2759814, 2893270, 2893271, 2893272, and 2829671.
However, physical properties of the image formation layers, which physical properties are required of the melt-type thermal transfer sheet, are different from those of the sublimation-type thermal transfer sheet in which organic pigments are used in the image formation layers. As a result, the problem that at the time of recording, optical density may decrease and the desired hues cannot be obtained remains unsolved in the melt-type thermal transfer sheets.